Journal Club 3

Dr Michael Mauk: Cerebellar Implementation of Movement Sequences Through Feedback

The Presenters

Manya

Aryan

Mahati

Tori

Brianna

Today’s Guest Speaker and Journal Club Publication

Title of Publication: Cerebellar Implementation of Movement Sequences Through Feedback

Where to find the publication: UT faculty website includes links to their publications. You may also find them on publication websites such as NIH or directly through their publishers.

Dr Michael Mauk

Research Interests

Mechanisms of learning and plasticity, Information processing in the cerebellum, Computer simulation of cerebellum

More info from directory

Before Jumping In…

What to look at by first glance:

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• Try to understand the title. It will usually make more sense when you get a better understanding of the topic.

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• The abstract will summarize the study into a more digestible format.

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• The introduction prepares you for the body paragraphs.

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• The source: eLife Digest, which published this paper, includes a description of the paper which introduces the paper and makes it more digestible!

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• Don’t panic if you don’t understand the paper right away! It may take a couple re-readings to understand concepts. Anatomical names are long, but they are just words. Don’t force yourself to memorize names if you are just casually reading.

Title: Cerebellar Implementation of Movement Sequences Through Feedback

Cerebellar

known for coordinating motor functions and learning

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Implementation of Movement Sequences

explores the cerebellum's role in organizing or controlling the order and structure of motor actions

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Through Feedback

implies that feedback mechanisms—either sensory or motor—are key to how the cerebellum carries out this function

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What are feedback mechanisms?

processes in which a system self-regulates by using output or response information to adjust and maintain its function

Abstract

Background/Introduction

• Most movements are made of several smaller steps, not just one action.

Objective/Purpose

• People with cerebellum issues struggle with learning and doing these movement sequences.
• Most research has focused on how the cerebellum handles single actions.

Methods

• Eyelid conditioning is a type of classical conditioning where an animal learns to blink in response to a neutral stimulus

Results

• Feedback from one movement step can signal the next step to start.
• Recordings from cerebellum cells showed all parts of a sequence are processed in a similar way.

Conclusion

• The study shows that the cerebellum can use simple learning to connect and time movement steps.

Background/Introduction Most movements are not unitary, but are comprised of sequences. Objective/Purpose Although patients with cerebellar pathology display severe deficits in the execution and learning of sequences (Doyon et al., 1997; Shin and Ivry, 2003), most of our understanding of cerebellar mechanisms has come from analyses of single component movements. Methods Eyelid conditioning is a cerebellar-mediated behavior that provides the ability to control and restrict inputs to the cerebellum through stimulation of mossy fibers. We utilized this advantage to test directly how the cerebellum can learn a sequence of inter-connected movement components in rabbits. Results We show that the feedback signals from one component are sufficient to serve as a cue for the next component in the sequence. In vivo recordings from Purkinje cells demonstrated that all components of the sequence were encoded similarly by cerebellar cortex. Conclusion These results provide a simple yet general framework for how the cerebellum can use simple associate learning processes to chain together a sequence of appropriately timed responses.

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Introduction

Main Question: How does the cerebellum learn movement sequences (like dance steps)?

Key Background:

• Cerebellum is vital for movement
• Most studies only looked at single movements, not sequences

Three Possible Learning Mechanisms:

• Each movement has its own separate cue
• One long cue triggers different movements at different times
• One movement triggers the next movement

Approach:

• Conditioning Rabbit to blink in sequence
• Electrical stimulation to isolate cerebellar learning

Testing if completing movement 1 → triggers movement 2 → triggers movement 3 …

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eLife Digest

Big Picture

• Gymnastics: sequence of movements
• Cerebellum: responsible for helping us learn this sequence of movements

Aim of the Study

• Rabbits blink eyes on external, specific direction
• Rather than external signals, could these signals be internal?
• Might explain how the cerebellum pieces together movements in a sequence

Results

• Rabbits could respond to the initial signal, and then blink in response to that first blink
• Found in patterns of nervous activity
• Cerebellum could use feedback from one movement to cue in the second movement
• But does this only apply to movement? Can it apply to other forms of action, including thinking?

Results

Main Results:

• Rabbits learned to produce chain of blinks from single cue
• First blink triggered by external stimulus
• Second, third, fourth blinks triggered by previous blink
• Each blink served as feedback signal for next

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Supporting Evidence:

• Control experiments showed later blinks tied to first blink, not initial cue
• Worked across different muscles (left eye → right eye)
• Purkinje cell recordings showed similar activity patterns for all blinks

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Significance:

• Shows cerebellum can chain movements using internal feedback
• Same mechanisms for single & sequential movements
• Explains how cerebellum builds complex movement sequences

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The cerebellum uses feedback from one movement to trigger and time the next, creating learned sequences through “chaining”

Discussion

Summary:

• Associative learning: mossy fiber input + feedback signals using past movement components within a timed sequence
• Cerebellum learns/adapts to not just single-component movements but can take on complex movement sequences

Where do the feedback signals originate?

• Possibilities: deep cerebellar nucleus neurons (DCN) or proprioceptive information

Basal ganglia’s role

• Also implicated in learning/memory, could be studied further

Natural complex multi-joint movements: integrates sensory feedback, motor control and coordination

• More applicable to actual behavior, the study used simplified discrete responses
• Initial response of triggering movement = motor cortex
• Feedback signals from later cerebellar output + the actual movement that leads to cerebellar learning to basically refine the continuation of the movement sequence so motor cortex is better guided (coordination, timing)

Thanks for Listening!

Any Questions?

Feel free to suggest future journals

Or interested in presenting a topic related to neuroscience in the next JC